A number of automobile manufacturers offer systems as comfort and/or safety aids for driving, which include sensors aimed for performed functions related to these systems. Such systems include, but are not limited to, adaptive cruise control and lane departure warning. Adaptive cruise control (ACC) systems provide an adaptive vehicle speed control, based on sensing of another vehicle or target in front of the host vehicle within which the cruise control operates, for example to reduce host vehicle speed and maintain a set distance between the vehicles. Lane departure warning (LDW) systems sense when a vehicle is straying from one lane of traffic and entering another, and provide a warning to the driver. ACC and LDW systems typically utilize a video camera, radar or laser sensor or the like to detect the presence of and distance to a target vehicle and/or traffic lane markings leading the host vehicle on which the sensor and the ACC or LDW system are mounted. Such sensors are now commonly mounted on motor vehicles, such as cars, trucks, lorries, vans and the like, and are typically located to the front of the host vehicle, and direct a video camera, radar or laser beam in the direction of forward motion of the motor vehicle.
In order for a system such as an ACC or LDW system to operate properly, the sensor must be adjusted (i.e., “aimed”) relative to the vehicle; for example, certain ACC and LDW sensors must be accurately aligned with a longitudinal line of the vehicle, such as the vehicle thrust line. The thrust line of a vehicle is determined by the toe of the rear wheels of the vehicle, and techniques for measurement thereof will be well known to those skilled in the art. It is a line that extends from the point of intersection of the rear transverse axis of the rear wheels and the longitudinal center line of the vehicle, and it extends forwardly of the vehicle at an angle to the center line of the vehicle. The angle that the thrust line makes with respect to the center line of the vehicle is determined by the toe of the rear wheels, and is relatively small; for example, as close to zero as possible.
It is well known to align the front and rear wheels of a vehicle with alignment devices or systems. Modern wheel alignment systems, providing increased accuracy and ease of use, have relied on visible targets and computer processing of camera images of the wheel mounted visible targets. Such systems are often referred to as 3D image wheel aligner systems. Examples of methods and apparatus involving computerized image processing for alignment of motor vehicles are described in U.S. Pat. No. 5,943,783 entitled “Method and apparatus for determining the alignment of motor vehicle wheels;” U.S. Pat. No. 5,809,658 entitled “Method and apparatus for calibrating cameras used in the alignment of motor vehicle wheels;” U.S. Pat. No. 5,724,743 entitled “Method and apparatus for determining the alignment of motor vehicle wheels;” and U.S. Pat. No. 5,535,522 entitled “Method and apparatus for determining the alignment of motor vehicle wheels.” A wheel alignment system of the type described in these references is sometimes called a “3D aligner” or “visual aligner.” An example of a commercial vehicle wheel aligner is the Visualiner 3D, commercially available from John Bean Company of Conway, Ark., a unit of Snap-on Inc.
Devices for aligning sensors, such as an axis of an ACC or LDW sensor, are also known, and generally include an alignment element such as a mirror or an optical target carried by a stand to be placed in front of the vehicle in the line of sight of the sensor. Such stands typically are not connected to the vehicle, and can have wheels to allow them to be easily moved. To perform a sensor alignment, the alignment element must be positioned and oriented accurately in front of the vehicle according to the vehicle manufacturer's specifications. Depending on the manufacturer's specifications, the alignment element may have to be adjusted in up to six different degrees of freedom; e.g., distance in front of the vehicle, left-to-right centering, perpendicularity to the thrust line, height, orientation about a horizontal axis, and orientation about an axis along the thrust line.
Techniques for using a visual aligner system to adjust an alignment element perpendicular to a vehicle thrust line are described in U.S. Pat. No. 6,823,601, entitled “Apparatus for use with a 3D image wheel aligner for facilitating adjustment of an adaptive cruise control sensor on a motor vehicle,” and U.S. Pat. No. 7,121,011, entitled “Camera technique for adaptive cruise control (ACC) sensor adjustment.” However, it would be advantageous to use a 3D image wheel aligner to adjust an alignment element in other degrees of freedom, because certain sensors require alignment element(s) to be adjusted in multiple degrees of freedom before being aligned. For example, LDW sensors require accurate positioning and orientation in at least three degrees of freedom; i.e., distance in front of the vehicle, left-to-right centering, and perpendicularity to the thrust line.
Hence, a need exists for a technique for use with a visual aligner system, such as used for wheel alignments, to allow the aligner to also position a fixture relative to a host vehicle in more than one degree of freedom.